The present invention relates to an apparatus and method for in-line cutting and replacement of a plastic pipe section particularly where the fluid being carried in the pipe must be maintained for supply to the user and, more specifically, to an arrangement for protecting the operators of the apparatus from contact with the fluid being conveyed.
In many commercial, municipal and industrial environments, plastic pipe conduits used to convey fluids to a site inevitably require repair, modification or replacement sometimes after many years of use. Such pipes are typically made from a thermoplastic polyvinylcholoride (PVC), polyethylene or other plastic formulations. Where the fluids being conveyed are flammable, at high temperatures or pressures and where the end user cannot tolerate any significant down time to shut-off of the flow through a conduit, the prior art has endeavored to provide in-line replacement and repair devices which bypass the section of the pipe being replaced or repaired temporarily with a bypass housing that typically includes an upstream connector and a downstream connector which enable operators to bypass a section of pipe while work is done. Such devices, however, present several disadvantages in use. First among these are the time required to install and then remove the bypass housing. Also, many of these housings have been difficult to set in place due to their size and effective sealing of the housing to assure worker safety has been a problem due in some respects to the rough handling of these devices in the field.
The present invention overcomes the foregoing as well as other difficulties in the prior art by providing an improved housing which an be easily handled by even an untrained crew and easily set in place to carry out a pipe repair or replacement operation. In one embodiment, a sealable housing is provided in two parts. One part is mounted about the pipe section to be replaced and also carries sealing elements and manipulating elements as well as a substitute pipe section. With the housing closed in a sealed manner, pipe cutters, carried on one of the housing parts are activated to cut the original pipe section at two locations in the sealed housing. A pipe shifting device carried in the housing is then shifted laterally to bring the new pipe section into alignment with the two cut ends of the original pipe line. The manipulating elements are then activated to move the two sealing collars outwardly to engage the cut ends of the original pipe line. Sealing of the collars respectively to the two cut ends of the original pipe line is then effected. In a preferred method, this is accomplished by supplying electrical current to two resistance wires embedded in the collars so as to heat the collars to a temperature sufficient to provide a plastic flow to achieve a seal between each collar and the engaged cut end of the original pipe upon cooling of the collar material. It will be understood, of course, that other sealing techniques may be employed.
It will be understood that the apparatus of the present invention can be operated without interrupting flow from the source to the user by virtue of the use of the sealed housing which is operable without external interference. Also, the replacement operation can be carried out independent of the orientation of the housing thus facilitating replacements in difficult terrain.
The foregoing and other advantages will become apparent as consideration is given to the following description taken in conjunction with the accompanying drawings, in which.